path: root/drivers/net/sfc/rx.c

/****************************************************************************
 * Driver for Solarflare Solarstorm network controllers and boards
 * Copyright 2005-2006 Fen Systems Ltd.
 * Copyright 2005-2009 Solarflare Communications Inc.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published
 * by the Free Software Foundation, incorporated herein by reference.
 */

#include <linux/socket.h>
#include <linux/in.h>
#include <linux/ip.h>
#include <linux/tcp.h>
#include <linux/udp.h>
#include <net/ip.h>
#include <net/checksum.h>
#include "net_driver.h"
#include "efx.h"
#include "nic.h"
#include "selftest.h"
#include "workarounds.h"

/* Number of RX descriptors pushed at once. */
#define EFX_RX_BATCH  8

/* Size of buffer allocated for skb header area. */
#define EFX_SKB_HEADERS  64u

/*
 * rx_alloc_method - RX buffer allocation method
 *
 * This driver supports two methods for allocating and using RX buffers:
 * each RX buffer may be backed by an skb or by an order-n page.
 *
 * When LRO is in use then the second method has a lower overhead,
 * since we don't have to allocate then free skbs on reassembled frames.
 *
 * Values:
 *   - RX_ALLOC_METHOD_AUTO = 0
 *   - RX_ALLOC_METHOD_SKB  = 1
 *   - RX_ALLOC_METHOD_PAGE = 2
 *
 * The heuristic for %RX_ALLOC_METHOD_AUTO is a simple hysteresis count
 * controlled by the parameters below.
 *
 *   - Since pushing and popping descriptors are separated by the rx_queue
 *     size, so the watermarks should be ~rxd_size.
 *   - The performance win by using page-based allocation for LRO is less
 *     than the performance hit of using page-based allocation of non-LRO,
 *     so the watermarks should reflect this.
 *
 * Per channel we maintain a single variable, updated by each channel:
 *
 *   rx_alloc_level += (lro_performed ? RX_ALLOC_FACTOR_LRO :
 *                      RX_ALLOC_FACTOR_SKB)
 * Per NAPI poll interval, we constrain rx_alloc_level to 0..MAX (which
 * limits the hysteresis), and update the allocation strategy:
 *
 *   rx_alloc_method = (rx_alloc_level > RX_ALLOC_LEVEL_LRO ?
 *                      RX_ALLOC_METHOD_PAGE : RX_ALLOC_METHOD_SKB)
 */
static int rx_alloc_method = RX_ALLOC_METHOD_AUTO;

#define RX_ALLOC_LEVEL_LRO 0x2000
#define RX_ALLOC_LEVEL_MAX 0x3000
#define RX_ALLOC_FACTOR_LRO 1
#define RX_ALLOC_FACTOR_SKB (-2)

/* This is the percentage fill level below which new RX descriptors
 * will be added to the RX descriptor ring.
 */
static unsigned int rx_refill_threshold = 90;

/* This is the percentage fill level to which an RX queue will be refilled
 * when the "RX refill threshold" is reached.
 */
static unsigned int rx_refill_limit = 95;

/*
 * RX maximum head room required.
 *
 * This must be at least 1 to prevent overflow and at least 2 to allow
 * pipelined receives.
 */
#define EFX_RXD_HEAD_ROOM 2

static inline unsigned int efx_rx_buf_offset(struct efx_rx_buffer *buf)
{
	/* Offset is always within one page, so we don't need to consider
	 * the page order.
	 */
	return (__force unsigned long) buf->data & (PAGE_SIZE - 1);
}
static inline unsigned int efx_rx_buf_size(struct efx_nic *efx)
{
	return PAGE_SIZE << efx->rx_buffer_order;
}


/**
 * efx_init_rx_buffer_skb - create new RX buffer using skb-based allocation
 *
 * @rx_queue:		Efx RX queue
 * @rx_buf:		RX buffer structure to populate
 *
 * This allocates memory for a new receive buffer, maps it for DMA,
 * and populates a struct efx_rx_buffer with the relevant
 * information.  Return a negative error code or 0 on success.
 */
static int efx_init_rx_buffer_skb(struct efx_rx_queue *rx_queue,
				  struct efx_rx_buffer *rx_buf)
{
	struct efx_nic *efx = rx_queue->efx;
	struct net_device *net_dev = efx->net_dev;
	int skb_len = efx->rx_buffer_len;

	rx_buf->skb = netdev_alloc_skb(net_dev, skb_len);
	if (unlikely(!rx_buf->skb))
		return -ENOMEM;

	/* Adjust the SKB for padding and checksum */
	skb_reserve(rx_buf->skb, NET_IP_ALIGN);
	rx_buf->len = skb_len - NET_IP_ALIGN;
	rx_buf->data = (char *)rx_buf->skb->data;
	rx_buf->skb->ip_summed = CHECKSUM_UNNECESSARY;

	rx_buf->dma_addr = pci_map_single(efx->pci_dev,
					  rx_buf->data, rx_buf->len,
					  PCI_DMA_FROMDEVICE);

	if (unlikely(pci_dma_mapping_error(efx->pci_dev, rx_buf->dma_addr))) {
		dev_kfree_skb_any(rx_buf->skb);
		rx_buf->skb = NULL;
		return -EIO;
	}

	return 0;
}

/**
 * efx_init_rx_buffer_page - create new RX buffer using page-based allocation
 *
 * @rx_queue:		Efx RX queue
 * @rx_buf:		RX buffer structure to populate
 *
 * This allocates memory for a new receive buffer, maps it for DMA,
 * and populates a struct efx_rx_buffer with the relevant
 * information.  Return a negative error code or 0 on success.
 */
static int efx_init_rx_buffer_page(struct efx_rx_queue *rx_queue,
				   struct efx_rx_buffer *rx_buf)
{
	struct efx_nic *efx = rx_queue->efx;
	int bytes, space, offset;

	bytes = efx->rx_buffer_len - EFX_PAGE_IP_ALIGN;

	/* If there is space left in the previously allocated page,
	 * then use it. Otherwise allocate a new one */
	rx_buf->page = rx_queue->buf_page;
	if (rx_buf->page == NULL) {
		dma_addr_t dma_addr;

		rx_buf->page = alloc_pages(__GFP_COLD | __GFP_COMP | GFP_ATOMIC,
					   efx->rx_buffer_order);
		if (unlikely(rx_buf->page == NULL))
			return -ENOMEM;

		dma_addr = pci_map_page(efx->pci_dev, rx_buf->page,
					0, efx_rx_buf_size(efx),
					PCI_DMA_FROMDEVICE);

		if (unlikely(pci_dma_mapping_error(efx->pci_dev, dma_addr))) {
			__free_pages(rx_buf->page, efx->rx_buffer_order);
			rx_buf->page = NULL;
			return -EIO;
		}

		rx_queue->buf_page = rx_buf->page;
		rx_queue->buf_dma_addr = dma_addr;
		rx_queue->buf_data = (page_address(rx_buf->page) +
				      EFX_PAGE_IP_ALIGN);
	}

	rx_buf->len = bytes;
	rx_buf->data = rx_queue->buf_data;
	offset = efx_rx_buf_offset(rx_buf);
	rx_buf->dma_addr = rx_queue->buf_dma_addr + offset;

	/* Try to pack multiple buffers per page */
	if (efx->rx_buffer_order == 0) {
		/* The next buffer starts on the next 512 byte boundary */
		rx_queue->buf_data += ((bytes + 0x1ff) & ~0x1ff);
		offset += ((bytes + 0x1ff) & ~0x1ff);

		space = efx_rx_buf_size(efx) - offset;
		if (space >= bytes) {
			/* Refs dropped on kernel releasing each skb */
			get_page(rx_queue->buf_page);
			goto out;
		}
	}

	/* This is the final RX buffer for this page, so mark it for
	 * unmapping */
	rx_queue->buf_page = NULL;
	rx_buf->unmap_addr = rx_queue->buf_dma_addr;

 out:
	return 0;
}

/* This allocates memory for a new receive buffer, maps it for DMA,
 * and populates a struct efx_rx_buffer with the relevant
 * information.
 */
static int efx_init_rx_buffer(struct efx_rx_queue *rx_queue,
			      struct efx_rx_buffer *new_rx_buf)
{
	int rc = 0;

	if (rx_queue->channel->rx_alloc_push_pages) {
		new_rx_buf->skb = NULL;
		rc = efx_init_rx_buffer_page(rx_queue, new_rx_buf);
		rx_queue->alloc_page_count++;
	} else {
		new_rx_buf->page = NULL;
		rc = efx_init_rx_buffer_skb(rx_queue, new_rx_buf);
		rx_queue->alloc_skb_count++;
	}

	if (unlikely(rc < 0))
		EFX_LOG_RL(rx_queue->efx, "%s RXQ[%d] =%d\n", __func__,
			   rx_queue->queue, rc);
	return rc;
}

static void efx_unmap_rx_buffer(struct efx_nic *efx,
				struct efx_rx_buffer *rx_buf)
{
	if (rx_buf->page) {
		EFX_BUG_ON_PARANOID(rx_buf->skb);
		if (rx_buf->unmap_addr)